The 1972 Flood caused a loss of life, widespread destruction, but as the waters receded it revealed the community's resilience.
Today's Remembrance Ceremony is about preparing for the future, but remembering the past.
Rapid City leaders have transformed the look of the city in the last 40 years.
Larry Lytle, the 1972 President of the City Council, said Saturday was about celebrating the cities growth, remembering those who perished, but also preparing for a future flood.
Lytle says it's not if, but when another flood will hit the city.
And while June 9th 1972 was Rapid City's darkest hour, it may have also been its citizen's finest moment.
"It was the greatest cooperation I've ever seen before that and since then. We had 100% cooperation of every man, woman, and child in Rapid City. There was nobody that disagreed, we worked shoulder to shoulder and knee to knee, and got the job done," said Lytle.
Lytle says if the past is any indication, the people of Rapid City will prove themselves as resilient as ever.